Aluminum alloy gun barrel with a lubricating film



ALUMINUM ALLOY GUN BARREL WITH A LUBRICATING FILM Filed March 24, 1955 G. c. SULLIVAN Senf-9, 195s INVENTOR.

United States ALUMINUM ALLOY GUN BARREL WITH A LUBRICATING FILM George C. Sullivan, Hollywood, Calif. Application March 24, 1953, Serial No. 344,401

6 Claims. (Cl. 42-'76) This invention relates to a firearm or more particularly to a barrel construction wherein the design and materials employed are of such a nature that the resultant product is a minimum in weight. This is accomplished in such a manner that other factors necessary in a practical and successful gun barrel, such as strength and life, are not jeopardized.

` a continuation-in-part of my copending applications,

Serial No. 215,694 filed March 15, 1951, and now abandoned, and Serial No. 272,428 led February 19, 1952, which has matured into Patent No. 2,780,019.

The present invention also provides a method of making arearm barrel, or the like, comprising the steps of machining the barrel from an aluminum alloy blank,

' drilling a bore axially of the blank, the bore having a diameter slightly in excess of the required finished diameter, and hard-coating the surface of the bore to a dimension at least that required for nished bore diameter. In the case of firearms having low breech pressures, the alloy blank itself may be originally formed in a tubular shape by the use of various well known techniques, thus integrally containing a bore which can be finished as described hereinafter.

Sportsmen, as well as ordnance manufacturers, have made many attempts to reduce the weight in firearms, foiit is recognized that such a light-weight firearm would Y' be advantageous in many respects. Both the sportsman and the soldier will be less fatigued at the end of the day if he has carried less weight. Efforts have been made in the past to decrease action or receiver, stock and sights weight but little, if any, has been attained in reducing barrel weight. This invention discloses a construction and method of manufacture of a gun barrel of reducedl weight, yet is of sucient material cross-section to minimize barrel whip.

-As the weight of a firearm is reduced, the recoil normally increases. .While it has been found that the increase in recoil is not fatiguing to the average shooter, it may be found desirable to provide a` recoil minimizing device. This invention is particularly advantageous in that the decreased weight of the basic material in the barrel will allow a larger barrel cross-section which decreases barrel whip and therefore increases shooting accuracy. This larger barrel cross-section can be carried to the muzzle, thus permitting the use of a muzzle brake orblast device which can be designed into and form a part of the barrel itself. rthis feature permits a construction that is streamlined, pleasing to the eye in comparison to present devices, economical of manufacture barrel which is advantageous in the event of a military' weapon and its accompanying bayonet.

Among the objects achieved in the present invention are the provision of a gun barrel construction in which preferably a non-ferrous alloy is used in conjunction with a hard-plated barrel or bore; a sleeve or liner being incorporated near the chamber of the barrel if desired. The preferred alloy is comprised essentially of aluminum combined with one or more group metals such as zinc, magnesium and copper. For instance, a material dis covered to he practical and workable in this application has the following constituents; aluminum 88.5%, magnesium 2.5%, zinc 5.5%, copper 1.5%, chromium 0.30%; the remainder consisting of impurities. Obviously, these metals can be varied within reasonable limits without the resultant material being affected. A preferred material of this type is a wrought alloy which has received solution heat treatment and elevated temperature aging, and is formed by rolling or preferably by extrusion processes. An alternate aluminum alloy material which may be preferred later is one in which the amount of alloying metals, notably magnesium and zinc, has been increased over that disclosed above. This material is stronger in that the ultimate tensile strengths have been increased approximately 8% to date, such material being somewhat experimental in nature at the present time.

These materials are particularly advantageous in that they are not only light in weight (.10 pound/cubic inch versus .28 pound/cubic inch) when compared to highstrength steels, but have greater thermal conductivity factors (.30 versus .10); the latter fact being of value in the minimization of firing temperatures. This material in combination with cooling ns which may be extruded originally or machined later about the chamber area, will provide excellent cooling of the barrel.

I have found that a barrel of the above mentioned material will not withstand repeated tiring unless a hardplating is applied to its internal bore. To that end, I propose the use of a chromium or a hard anodic, or the like, plating. For instance, a typical method of chromium plating would be to insert an anode or cathode bar through the bore of the barrel and immerse the combination in an electrolyte for the plating operation; all in accordance with well-known current procedure. The barrel should be anodized first and then ground to remove the oxide below the area to be plated. It may be desirable to give the barrel a flash of copper or nickel to seal the alloy material from water penetration causing corrosion and to prepare a better bonding surface for the chromium plate. The plating is then applied by standard methods. It has been found wise to rotate the barrel during the plating operation to minimize the possibility of uneven plating thickness.

Effort is made to control the thickness of the plating in order to eliminate subsequent machine operations; however, it is to be understood that the plating can be increased and later reduced to finish Idimensions by polishing, grinding, teaming, honing, or the like, machine operations.

Another type of hard-coating has been applied to the bore with great success, such coating being applied by an electro-chemical process which creates a non-metallic,

f hard, heat and corrosion resistant surface which is integral with the base material, no usually requiring the use of a separate plating metal, as described above. One type coating can be created by passing a current through an oxidizing solution,

the time of operation and intensity of current determining principally the thickness of the coating obtained, such coating being termed as surface oxidation. A coating recently developed by the Glenn L. Martin Company and described in trade journals, will provide a hard, practical coating for the gun barrel of this invention; such coating having been found to be excellent. Other companies have recently improved their anodizing tretaments to the point that such anodized coating may produce a sufiiciently hard, dense and corrosion resistant surface as to be satisfactory. These coatings, usually being composed of amorphous alumina (A1203), offer very good resistance to wear and abrasion, and are valuable in that it is highly refractory in nature, offering resistance to high temperatures.

A coating treatment which has resulted in a'fine product consists of an electrolytic bath containing principally sulphuric acid, the temperature of which has been lowered to approximately 30 to 32 F. The use of carbon dioxide as a temperature reducing medium has been found to be excellent in that the carbon dioxide not only performs a refrigerating function but enters into the reaction in such a way that the resultant composition of coating has extremely good resistance to wear. Oxalic acid can be added to the bath solution thus permitting higher bath temperatures and resultant lowered costs of operation, but the coating may suffer some in physical characteristics.

The hard coating type of process, distinguishable from the plating process in that the hard coating is formed from the basic material of the barrel itself instead of depositing a plating of another material on the barrel, is advantageous in that there is a surface impregnation which renders a highly efiicient joint action between the hard coating and the basic material of the barrel. In this process a dimensional growth may be associated with the formation of the hard oxide films, and this feature should be taken into consideration in the design of the barrel. The oxide surface, although extremely hard, can be finished by honing, lapping, or the like, methods to produce very smooth surfaces.

I have found that the plating and coating treatments hereinbefore disclosed are very satisfactory, however, a further improvement can be made by subjecting the processed barrel to an additional procedure which, in effect, produces a barrel having an outside solid film which is particularly advantageous in its good lubricating qualities. This film provides a long lasting, all-Weather, non-greasy or oily surface which further resists erosion and corrosion and at the same time dry lubricates the barrel.

Oils and greases have been applied for years in an effort to minimize corrosion, but such are difficult to use, are temporary in application, are impractical in extremely cold or hot weather, tend to pick up extraneous matter such as sand and the like, and thus have little utility for all-around use. The dry lubricant film of this invention eliminates these undesirable features.

While this dry lubricant is effective with several types of materials or coatings, I have found it to be particularly advantageous with the surface impregnation type of coating as disclosed herein. This process results in a surface coating having a granular structure which is quite porous. Thus the hard coating of the surface forms an excellent foundation for the dry lubricant film, which not only imbeds itself in the pores of the metal but actually plates out on the metal friction surfaces. Due to the resultant dry lubricant film, there is always lubrication on the surfaces Which cannot drain away, squeeze out, freeze up or become contaminated with foreign matter.

A gun barrel when treated according to the processes above described has excellent resistance to corrosion and erosion and if designed with taper its performance can be substantially improved. The dry lubricant film further enhances the utility and performance of the barrel.

With the above and other objects in view, those skilled in the art will appreciate the advantages and the invention '4 as disclosed herein, after reviewing the accompanying drawings wherein:

Figure 1 is a side View of a typical barrel incorporating the present invention in part; Figure l being shown in an enlarged and cross-sectioned manner;

Figure 2 is a cross-sectional view of the barrel showing details 0f the plating or hardecoating and including the provision of a sleeve or liner;

Figure 3 is a sectional view of the barrel showingthe plating or coating applied to the bore;

Figure 4 is an elevational cross-sectioned view of the chamber portion of the barrel, showing an alternate liner;

Figure 5 is a sectional view of the barrelshowing said alternate liner;

Figure 6 is a sectional View of the muzzle end of the barrel showing an integral recoil minimizing device, including the plating or hard-coating and the dry lubricant film of this invention;

Figure 7 is a sectional view of an alternate design of barrel in which the chamber is incorporated in a liner, cooling fins provided about the chamberV area, and the bore being so processed that it is provided with a tapered internal diameter;

Figure 8 shows a general method of'hard plating the barrel and obtaining a tapered bore if desired; and

Figure 9 is an enlarged sectional view of Figure 6 showing both the plating or hard-coating and the dry lubricant film of this invention.

As shown in the drawings, the composite barrel of the present invention includes a barrel body 10 formed of a lightweight material such as aluminum alloy, having the usual bore 11 which may be ried in the usual manner to provide interior helical-like lands 12 and grooves 13. The barrel 10 is provided at its rear end with anV externally threaded shank 14 or other typical means ,by which the barrel may be attached to the action or receiver.

The barrel 10, and particularly the bore 11, is coated.

with a hard-coating 15. While it is essential, or at least to the chamber 16 to assist in preventing erosion therein, however, the chamber 16 and the threads 14 can .be blocked off or masked by using a vinyl tape or the like,

thus preventing interference with prior machining` to... close tolerances and head-spacing of the barrel and` The barrel can, if desired, be substantially maaction. chine finished prior to plating or coating, leaving .001

to .004 inch or less tolerance for the thickness of theV coating to be applied.

The rear end of the barrel 10 contains the usual charnber 16, the size and shape of which is determined by the cartridge and caliber used. The explosion pressures are a maximum in the area of the chamber 16 and reduce in the direction of the muzzle 17. While available light weight metals have been found to have sufficient strength to withstand with safety the explosion pressures encountered, it may be advisable, if a barrel of exceedingly low weight is wanted, to incorporate a sleeve 18 around the chamber 16 area where pressures are at a maximum. An alternate sleeve or liner 19 may be incorporated adjacent the chamber 16; this typey of strengthening element having the additional advantage of being removable and replaceable in event of excessive erosion dueto repeated firing. Both the sleeve 18 and the liner 19 may be installed by sweating the parts together or by furnace brazing, or by other standard fastening means.

In the first case, the heat producedas a result of firing y tends to increase joint efficiency action and thus permit each element to absorb yits proportion of the stresses produced. The sleeve 18 can drop into detents 20 for.

securityand the liner 19 can be secured by conventional means, such as threading and the like.

The sleeve 18 or liner 19 is preferably made of a highstrength metal such as stainless steel, which has a tensile strength approaching 125,000 pounds per square inch, or a titanium alloy having a tensile strength in excess of 150,000 pounds per square inch; the latter having the additional advantage of light weight. High strength ferrous materials may also be used. A typical material ofthe titanium type is a titanium alloy containing approximately chromium and 3% aluminum as produced by the P. R. Mallory Company; other comparable titanium alloys being produced now by the Remington Company.

The muzzle 17 can, if desired, be constructed with a recoil absorbing device, as disclosed in Figure 6. The blast chamber 21 can be formed in several ways, by undercutting from the muzzle end of the barrel or by drilling a hole 22 and inserting a plug 23 therein; the plug 23 having an inside diameter slightly greater than the groovediameter of the bore 11 and being attached by conventional means such as threading 24, or the like. Blast holesl 25 are drilled through the barrel 11 to provide gas exit and recoil absorption. Figure 6 shows the plating or hard coating being applied not only to the bore 11 but also to the outside of the barrel. Figure 6 also showsV a dry lubricant film 40 which can be applied to the coating 15; the combination of the coating and film being particularly meritorious.

The method of manufacture as disclosed by this invention is particularly advantageous in that it lends itself well to the production of a barrel having a tapered borje if so desired, such a tapered bore being obtained in a very economical manner when compared with other fabrication processes. In the alternate design of Figure 7, a barrel 26 incorporates a liner 27 constructed of a high strength material. The barrel 26 includes fins 28 about the chamber area for cooling purposes. The liner 27 Acan be attached to the barrel 26 by conventional means;

the attachment shown in Figure 7 including a series of splines 29 to insure proper alignment of the riings 30 and 31 at the joint 32. The liner 27 is firmly attached to' the remaining portion of the barrel by means of threads 33 and coupling 34. It is to be understood that the liner 27 can be secured to the barrel proper by direct threading therebetween or by other means. Figure 7 shows, in an exaggerated manner, a plating or hard coating 35 which is comparatively thin adjacent the chamber of the barrel and which gradually increases in thickness as the muzzle is approached. This tapering effect is advantageous in that the accuracy of the barrel is improved considerably, while permitting the lowering of critical breech pressures, or the raising of bullet muzzle velocity. Tapered rifling is also of advantage in that with such a construction a bullet jacket can be fabricated of a harder material, thus allowing greater penetrating power.

The taper of the barrel bore is obtained as a result of the hard coating process, as shown by Figure 8. For example, the barrel 26, having a constant bore diameter as a result of machining procedures, is placed within a tank 36 which contains an electrolytic solution 37, as hereinbefore described. The barrel 26 is preferably inserted about a cathode rod 38 which may be negatively charged and which is spaced therefrom by appropriate techniques and means now employed in the plating industry. The barrel 26 may be positively charged to an anode in such a manner that a current flows through the electroyte 37 to accomplish the formation of the hard lcoating 35.

inasmuch as the formation of the coating is primarily a function of time of immersion, temperature of electrolyte and intensity or density of current applied, it will be seen out of the bath, by appropriate facilities such as a lifting means 39, thus producing a bore which may be tapered uniformly or non-uniformly in either direction in accordance with the most desired design of barrel.V The bore can be treated by inserting the total barrel into the solution at one time; the bore having a close fitting flexible plunger or piston which extends the length of the barrel and is slowly pulled therefrom to produce a tapered bore. After treatment the barrel is preferablytransferred to a cold water rinse to remove any residual electrolyte.

Figure 9, a sectional view of Figure 6, has been enlarged to point out the resultant plating or hard coating 15 and also the lubricant film 40; the latter may be applied to the barrel assembly, which may consist of the liner, bore, chamber or the inside or outside contour of the barrel as is desired. T-he film 40 can be varied both in formulation and ingredients, however, l have found that a preferred material comprises a formulated resin binder, graphite and molybdenum disulfide. A typical material would consist of (l) a binder (for instance, an epon or melmac resin base) amounting to approximately 225 parts by weight; (2) molybdenum disulfide (M052) in an amount approximating 225 parts by weight and (3) graphite (finely ground) in an amount approximating 25 parts by weight. These materials are ball milled together for a considerable length of time; say, at least one hundred hours, after which it is ready for use.

This material can be thinned with xylene or equivalent for ease in operation and application. It has been found that application by spray methods result in a good and consistent film; however, in the gun barrel of this invention I have found that dipping procedures are entirely satisfactory. The barrel can be dipped into a tank which contains the film material and removed slowly, after which it is allowed to air dry for at least fifteen minutes. if desired, a second film can then be applied by repeating the process. While it is not absolutely necessary, I have found it desirable to cure the film by baking in a controlled temperature environment at approximately 325 degrees Fahrenheit for at least a period of thirty minutes. This preferred treatment results in a film with a thickness of from one-eighth to one-half mil as may be required. By using an amine catalyst it is possible to cure the film at room temperatures, however, it takes considerable time and the film will not have as good heat stability as is provided by the baking procedure. The resultant dry lubricant film which takes advantage of the low frictional properties of molybdenum disulfide, provides a surface having a long life. If at a later date and it is so desired, the film process can be reapplied and the barrel is then renewed for all practical purposes.

While a rifle barrel has been chosen for illustration and description, it will be understood that the invention is equally applicable to machine guns, shot guns or small arms barrels, such as revolvers or automatics. It may be also applied to other types of firearms or ordnance where reduced weight is desirable, such as mobile field or tank guns, infantry mortars, recoilless rifies and the like. Smooth bore firearms are well adaptable to this process of manufacture.

It should be apparent that numerous modifications may be made without departing from the spirit of the invention as expressed in the claims.

I claim:

l. In a firearm, the combination of a barrel constructed of a lightweight high thermal conductivity aluminum alloy, a liner mounted in the chamber area of said barrel, a layer of porous material upon the surfaces of said barrel, and a substantially permanent, solid, lubricating film upon said porous layer which extends into the pores of said porous layer, said solid lubricating film comprising approximately 225 parts by weight of molybdenum disulfide, approximately 225 parts by weight of resinous binder, and approximately 25 parts by weight of graphite.

2. A firearm barrel made of light weight non-ferrous metal alloy having upon at least its bore surface a layer of porous material, and a substantially permanent dry lubricating film upon said porous layer which extends into the pores of said porous layer, said dry lubricating film comprising approximately 225 parts by Weight of binder, approximately 225 parts by Weight of molybdenum disulfide, and approximately 25 parts by Weight of graphite.

3. A firearm barrel made of a light Weight non-ferrous metal alloy having upon at least its bore surface a layer of porous material, said layer of porous material being composed essentially of an oxide of the metal which forms the major portion of the barrel, and a substantially permanent dry lubricating lm upon said porous layer which extends into the pores of said porous layer, said dry lubricating iilm comprising approximately 225 parts by Weight of binder, approximately 225 parts by Weight of molybdenum disulfide, and approximately 25 parts by Weight of graphite.

4. A firearm barrel assembly made of light Weight nonferrous metal alloy having upon at least its bore surface a layer of porous material, and a substantially permanent dry lubricating lin upon said porous layer which extends into the pores of said porous layer, said dry lubricating film comprising approximately 225 parts by Weight of binder, approximately 225 parts by Weight of molybdenum disulfide, and approximately 25 parts by Weight of graphite.

5. A rearm barrel madeV of light. Weight, `highthermal conductivity aluminum alloy having upon at least its bore surface, a layer of porous material, and a substantially permanent dry baked lubricating film upon said porous layer which extends into the pores of said porous layer, said dry baked lubricating lm comprising approximately 225 parts by Weight of binder, approximately 225 parts by Weight of molybdenum disulfide, and approximately 25 parts by Weight of graphite, said lm having a thickness of from Ms to 1/z mil.

6. A firearm part made of light weight aluminum al-V and approximately 25 parts of nely ground graphite,

said lilm having a thickness of from 1A; to 1/2 mil.

References Cited in the le of this patent UNITED STATES PATENTS 1,207,218 Roux Dec. 5, 1918 1,346,190 Fahrenwald July 13, 1920 2,104,319 Dicke Jan. 4, 1938 2,156,803 Cooper et al May 2, 1939 2,361,211 Kalischer Oct. 24, 1944 2,395,044 Gorton Feb. 19, 1946 2,413,022 Wood Dec. 24, 1946 2,440,634 Henney Apr. 27, 1948 2,466,642 Larsen Apr. 5, 1949 2,543,741 Zweifel Feb. 27, 1951 2,686,155 Willis et al. Aug. 10, 1954 2,736,119 Clarkson et al Feb. 28, 1956 FOREIGN PATENTS 831,030 France May 30, 1938 

5. A FIREARM BARREL MADE OF LIGHT WEIGHT, HIGH THERMAL CONDUCTIVITY ALUMINUM ALLOY HAVING UPON AT LEAST ITS BORE SURFACE, A LAYER OF POROUS MATERIAL, AND A SUBSTANTIALLY PERMANENT DRY BAKED LUBRICATING FILM UPON SAID POROUS LAYER WHICH EXTENDS INTO THE PORES OF SAID POROUS LAYER, SAID DRY BAKED LUBRICATING FILM COMPRISING APPROXIMATELY 225 PARTS BY WEIGHT OF BINDER, APPROXIMATELY 225 PARTS BY WEIGHT OF LOMYBDENUM DISULFIDE, AND APPROXIMATELY 25 PARTS BY WEIGHT OF GRAPHITE, SAID FILM HAVING A THICKNESS OF FROM 1/8 TO 1/2 MIL. 